Seatbelt retractor

ABSTRACT

A side wall portion of a housing is provided with an arm-protective extending portion below a pawl and a mechanical arm. The arm-protective extending portion extends inwardly at a substantially right angle. Further, a side wall portion of the housing is provided with a shaft-protective extending portion which extends inwardly from the lower edge portion of a horizontally long opening portion. The horizontally long opening portion is formed so as to face a coupling shaft over its full length. Below this shaft-protective extending portion, there is formed a bolt insertion hole through which a bolt is inserted at the time of mounting the housing to a fastening piece of a vehicle.

TECHNICAL FIELD

The present invention relates to a seatbelt retractor which removes the slack of webbing in case of an emergency such as vehicle collision or the like.

BACKGROUND ART

Conventionally, a seatbelt retractor for the front seat of a vehicle is housed inside a center pillar from an opening portion formed in a lower portion of an inner panel of the center pillar, and thereby mounted to a vehicle body.

For instance, as disclosed in Japanese Laid-open Patent Publication No. 2006-315572 (paragraphs 0015-0034, FIG. 1-FIG. 7), a fastening piece protruding upward is provided at the center position of the lower edge portion of an opening portion formed in the lower portion of an inner panel of a center pillar. Additionally, a screw hole is formed in the vicinity of the center position in the upper edge portion of this opening portion. The lower end portion of a base plate of the seatbelt retractor is fastened to the upper end portion of the fastening piece with a bolt and nut. The upper end portion of this base plate is fastened with a bolt and nut at the screw hole formed in the center position in the upper edge portion of the opening portion through a mounting plate member having a crank shape in cross section and formed so as to overhang the outside of the vehicle.

DISCLOSURE OF THE INVENTION

However, in the seatbelt retractor disclosed in the above-described patent publication, when a mechanical member is in the vicinity of the inner lower end portion of the base plate of the seatbelt retractor, at the time of mounting the base plate to the fastening piece protruding upward, the mechanical member may be brought into contact with this fastening piece and thereby cause damage to the seatbelt retractor. Furthermore, the mounting needs to be carried out with care so as to avoid contact between the fastening piece and the mechanical member. This makes it difficult to shorten the time required for the work of mounting.

The present invention has been made in view of the above-described problems and an object thereof is to provide a seatbelt retractor which can be mounted to a vehicle easily and has a high reliability.

The seatbelt retractor of the present invention which achieves the above-described object comprises: a take-up drum onto which a webbing is wound and housed; a housing which includes a first side wall portion and a second side wall portion facing the first side wall portion, and rotatably supports the take-up drum in between the first side wall portion and the second side wall portion; and a pretensioner assembly which rotates the take-up drum in a retracting direction to retract the webbing in case of vehicle collision. In such seatbelt retractor, the pretensioner mechanism includes a driving device which is mounted to an outside of the first side wall portion of the housing and causes the take-up drum to rotate in the retracting direction of the webbing in case of the vehicle collision. The take-up drum includes: a ratchet gear formed on a periphery of an edge portion of the take-up drum which so as to face an inside of the second side wall portion of the housing; a pawl arranged at a position where the pawl is disengaged from the ratchet gear while one end of the pawl is rotatably supported at the inside of the second side wall portion of the housing; and a locking device which is directly activated by the driving device upon activation of the driving device and locks the pawl in an engaged state with the ratchet gear. The locking device includes: an arm member one end of which is rotatably supported at an outside of the first side wall portion of the housing; a rotating device which is provided at the outside of the first wall portion of the housing and is directly activated by the driving device so as to cause the arm member to rotate in a predetermined direction; a depressing member which is in contact with the pawl at one side face which is opposed to other side face thereof which is closer to the ratchet gear while one end of the depressing member is rotatably supported at the inside of the second wall portion of the housing; and a coupling shaft which couples the arm member and the depressing member. The housing includes: a third wall portion which is opposed to a periphery of the coupling shaft; a bolt insertion hole which is formed in an opposite end portion of the third wall portion with respect to a pull-out direction of the webbing, the bolt insertion hole being provided for mounting the housing to a vehicle; a first extending portion for protecting the shaft which extends from the inside of the third wall portion so as to be opposed to a side of the coupling shaft which is closer to the bolt insertion hole.

In such a seatbelt retractor, the bolt insertion hole is formed in the end portion of the third side wall portion which is opposed to the periphery of the coupling shaft so as to mount the housing to the vehicle therethrough. Further, the first extending portion for protecting the shaft extends from the inside of the third side wall portion so as to face the bolt insertion hole side of the coupling shaft.

Accordingly, when fastening the bolt insertion hole formed in the end portion of the third side wall portion to the upper end portion of the fastening piece in the opening portion formed in the lower portion or the like of the center pillar with a bolt and nut, the first extending portion for protecting the shaft can prevent contact between the fastening piece and the coupling shaft. This makes it possible to mount a seatbelt retractor to a vehicle easily. At the same time, it is possible to assuredly prevent damage such as bending of the coupling shaft when mounting to a vehicle, to thereby provide a seatbelt retractor with high reliability.

Further, if the driving device of the pretensioner assembly is activated, this driving device directly activates the rotating device which rotates the arm member arranged at the outside of the first side wall portion of the housing in a predetermined direction. Therefore, substantially at the same time as the activation of the driving device, it is possible to directly activate the pawl arranged at the inside of the second side wall portion of the housing through the arm member, the coupling shaft and the depressing member and lock this pawl in the engaged state with the ratchet gear rapidly and reliably.

Further, in the seatbelt retractor of the present invention, the housing preferably includes a second extending portion for protecting the depressing member which extends from the inside of the second side wall portion of the housing so as to protect one side face of the depressing member which is opposed to other side face thereof which is closer to the pawl.

Further, in such a seatbelt retractor, the second extending portion for protecting the depressing member extends from the inside of the second side wall portion of the housing so as to protect one side face of the depressing member which is opposed to other side face thereof which is closer to the pawl, the depressing member being arranged at the inside of the second wall portion. Thus, when fastening the bolt insertion hole formed in the end portion of the third side wall portion opposed to the periphery of the coupling shaft to the upper end portion of the fastening piece in the opening portion formed in the lower portion or the like of the center pillar with a bolt and nut, it is possible to prevent contact between the fastening piece and the depressing member. This makes it possible to mount a seatbelt retractor to a vehicle easily. At the same time, it is possible to assuredly prevent damage of the depressing member when mounting to a vehicle, to thereby provide a seatbelt retractor with higher reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an outer appearance of a seatbelt retractor according to a present embodiment;

FIG. 2 is a perspective view showing respective assemblies of the seatbelt retractor in a disassembled state;

FIG. 3 is a perspective view of a take-up drum unit;

FIG. 4 is a cross-section view of the seatbelt retractor;

FIG. 5 is an exploded perspective view of the take-up drum unit, a pretensioner unit and a take-up spring unit;

FIG. 6 is a perspective view of a pretensioner unit as seen from a housing unit mounting side thereof;

FIG. 7 is a side view showing the pretensioner unit;

FIG. 8 is an exploded perspective view showing the pretensioner unit in FIG. 6 in a disassembled state;

FIG. 9 is an exploded perspective view of a housing unit;

FIG. 10 is a side view showing the seatbelt retractor with the locking unit removed therefrom;

FIG. 11 is an explanatory diagram showing a state that a piston is moved in response to the activation of a gas generating member of the pretensioner mechanism and the lower end portion of a rotating lever is disengaged from the tip end portion of a gear-side arm; and

FIG. 12 is an explanatory diagram showing a pawl operation corresponding to FIG. 11.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, one embodiment of the seatbelt retractor according to the present invention will be described in detail while referring to the accompanying drawings.

[Schematic Configuration]

First, a schematic configuration of a seatbelt retractor 1 according to the present embodiment will be described based on FIG. 1 and FIG. 2.

FIG. 1 is a perspective view showing an outer appearance of a seatbelt retractor 1 according to the present embodiment. FIG. 2 is a perspective view showing the respective assemblies of the seatbelt retractor 1 in a disassembled state.

As shown in FIG. 1 and FIG. 2, the seatbelt retractor 1 is a device for retracting a vehicle webbing 3. The seatbelt retractor 1 is comprised of a housing unit 5, a take-up drum unit 6, a pretensioner unit 7, a take-up spring unit 8 and a locking unit 9.

The locking unit 9 is fixed to a side wall portion 12 of a housing 11 constituting the housing unit 5 as will be described later. The locking unit 9 carries out an actuating operation to stop pull out of the webbing 3 in response to a sudden pull out of the webbing 3 or more than predetermined acceleration of a vehicle speed.

The pretensioner unit 7 having a pretensioner mechanism 17 (refer to FIG. 6) as will be described later is mounted to the housing unit 5. To be more specific, the housing unit 5 has a substantially U-shape in plain view and has a side wall portion 13 and a side wall portion 14 which constitute opposite sides thereof. From the top and lower edge portions of the side wall portions 13 and 14, screwed portions 13A, 13B and screwed portion 14A, 14B extend inwardly from each side wall portion 13 and 14 roughly at right angle and form a screw hole separately. The pretensioner unit 7 and the housing unit 5 are screwed with three screws 15 and a stopper screw 16 at the screwed portions 13A, 13B, 14A, and 14B. Thereby, the pretensioner unit 7 constitutes the other side wall portion opposite the side wall portion 12 of the housing 11.

A take-up spring unit 8 is fixed to an outer side of the pretensioner unit 7 by nylon latches 8A which are integrally formed with a spring case 56 (refer to FIG. 5).

A take-up drum unit 6 onto which the webbing 3 is wound is rotatably supported between the pretensioner unit 7 and the locking unit 9 fixed to the side wall portion 12 of the housing unit 5.

[Schematic Configuration of Take-Up Drum Unit]

Next, a schematic configuration of the take-up drum unit 6 will be described based on FIG. 2 through FIG. 5.

FIG. 3 is a perspective view of a take-up drum unit 6. FIG. 4 is a cross-section view of a seatbelt retractor 1. FIG. 5 is an exploded perspective view of the take-up drum unit 6, the pretensioner unit 7 and the take-up spring unit 8.

As shown in FIG. 2 through FIG. 5, the take-up drum unit 6 is comprised of a guiding drum 21, a drum shaft 22, a torsion bar 23, a wire 24, a wire plate 25, a ratchet gear 26 and a bearing 32.

The guiding drum 21 is made of an aluminum material or the like and is formed in a substantially cylindrical shape, with one end portion thereof facing to the pretensioner unit 7 being walled and closed. On an edge portion of a shaft central direction of the guiding drum 21 which is at the side of pretensioner unit 7, there is formed a flange portion 27 which extends radially and outwardly from an outer peripheral portion of the guiding drum 21, roughly at a right angle with its shaft central direction. A clutch gear 30 is formed in an inner peripheral face of this flange portion 27 so that the clutch gear 30 engages the respective clutch pawls 29 in case of vehicle collision as will be described later.

A cylindrical mounting boss 31 is erected at a central position in the end portion of the guiding drum 21 on the pretensioner unit 7 side. Also, a drum shaft 22 formed of a steel material or the like is mounted at the central position of this end portion by press fitting or the like. To the outer periphery of the mounting boss 31, there are fitted the bearing 32 which has a cylindrical portion 32A having substantially a cylindrical shape and being formed of a synthetic resin material such as polyacetal resin or the like, and a flanged end portion 32B which is connected at an outer periphery of a bottom end portion of the cylindrical portion 32A. The take-up drum unit 6 is rotatably supported by a shaft receiving portion 33A of a pinion gear body 33 (refer to FIG. 6 and FIG. 8) through this bearing 32. The pinion gear body 33 is formed of a steel material and the like and constitutes the pretensioner unit 7.

Inside the guiding drum 21, there is formed a shaft hole 21A which extends along a center axis thereof so as to become tapered as for the draft angle. Within the shaft hole 21A on the flange portion 27 side, there is formed a spline groove for fitting the torsion bar 23 which is made of a steel material or the like. The spline 23A side of the torsion bar 23 is inserted in the shaft hole 21A of the guiding drum 21 and is press-fitted to get in contact with the flange portion 27. As a result, the torsion bar 23 is press-fitted and fixed inside the guiding drum 21 so that relative rotation thereof with respect to the guiding drum 21 is disabled.

On the locking unit 9 side in an axial direction of the guiding drum 21, there is formed a flange portion 35 which extends slightly in a radial direction from an outer peripheral surface slightly inside an edge portion of the guiding drum 21. Also, from an outer side of the flange portion 35, there is formed a cylindrical stepped portion 36 of which outer diameter of a portion at an outer side thereof becomes tapered in an axial direction. A pair of ejector pins 37 and 37 are erected at radially opposite positions in an outer end portion of the stepped portion 36.

On an outer side surface of the flange portion 35, there is formed a convex portion in a predetermined shape. A rod-shaped wire 24 made up of a metallic material such as a stainless steel material is mounted to an outer periphery of a bottom end portion of the stepped portion 36 so as to match the shape of this convex portion.

An outer peripheral portion of the flange portion 35 is covered by a wire plate 25 which has a substantially egg-like shape in a side plan view. The wire plate 25 is made of an aluminum material or the like and has a convex portion 38 formed at an outer peripheral portion of its inner surface facing to the guiding drum 21. The convex portion 38 is fitted with a wire 24 which protrudes outward from the flange portion 35.

At a central part of the wire plate 25, there is formed a through hole 40 into which the stepped portion 36 will be inserted. On an outer edge portion of the through hole 40 at an outer side in an axial direction thereof, there are provided a pair of engaging convex portions 41 which have two convex portions formed thereon which protrude in a circular shape radially inwardly from an internal peripheral so as to oppose each other in a radial direction. On an outer edge portion at an outer side in an axial direction which is interposed between the respective engaging convex portions 41 of the through hole 40, there are erected four pairs of rivet pins 39 so as to oppose each other in a radial direction. A concave portion 39A being recessed to a predetermined depth in a semi-circular arcuate shape is formed in a bottom end portion of each rivet pin 39.

A ratchet gear 26 has a cylindrical extending portion 42 having a disk-like shape and being made of a steel material or the like. The extending portion 42 extends from an outer peripheral portion in an axial direction up to a length substantially the same with the stepped portion 36. In an outer peripheral surface of this extending portion 42, there is formed a ratchet gear portion 45 which is engaged with the pawl 43 in case of vehicle collision or vehicle emergency as will be described later (refer to FIG. 9). At an edge portion of the extending portion 42 in an axial direction on the guiding drum 21 side, there is formed a baffle flange 46 which extends from an outer peripheral portion in a radial direction. Further, a pair of engaging concave portions 46B are provided at an outer periphery of the baffle flange 46 (refer to FIG. 5) thereon so as to oppose each other in a radial direction. The engaging concave portions 45B each have two concave portions being recessed in a circular shape inwardly in a radial direction thereof. Concave portions 46A being recessed to a predetermined depth in a semi-circular arcuate shape are formed in an outer surface in the axial direction of the baffle flange 46, so as to oppose the respective rivet pins 39.

Through holes 47 are opened in the ratchet gear 26 at positions opposite the respective ejector pins 37 erected from the guiding drum 21 for inserting the respective ejector pins 37. Concave portions 47A being recessed to a predetermined depth are formed in the circumference of the through holes 47. A shaft portion 48 is erected at a center position outside of the ratchet gear 26. A spline 48A is formed at an outer peripheral surface of the shaft portion 48. The take-up drum unit 6 is thus rotatably supported by the locking unit 9 through this shaft portion 48.

A cylindrical mounting boss 49 is erected at a central part of an inner surface of the ratchet gear 26. Spline grooves are formed at an inner peripheral surface of the mounting boss 49 for fitting the spline 23B formed at the other end of the torsion bar 23. The spline 23 B formed at the other end of the torsion bar is formed so as to have an outer diameter which is approximately the same as the outer diameter of the spline 23A formed at the one end of the torsion bar 23.

Accordingly, the respective engaging concave portions 46B of the baffle flange 46 in the ratchet gear 26 are fitted with the respective engaging convex portions 41 of the wire plate 25. Thereafter, the respective rivet pins 39 are riveted so as to expand at an inner side of the concave portions 39A at a base end thereof and the concave portions 46A of the baffle flange 46 formed at opposite positions. The wire 24 is mounted to an outer surface of the flange portion 35 in the guiding drum 21. Next, when the wire plate 25 and the ratchet gear 26 are applied to the outside of the flange portion 35, the spline 23B formed at the other end of the torsion bar 23 is fitted inside the mounting boss 49 while the respective ejector pins 37 of the guiding drum 21 are being inserted inside the respective through holes 47 of the ratchet gear 26. Thereafter, the respective ejector pins 37 are riveted so as to be expanded inside the concave portions 47A formed in a circumference of the through holes 47.

As a result, the ratchet gear 26 and the wire plate 25 are mounted so that relative rotation thereof is disabled. This ratchet gear 26 and the wire plate 25 are also mounted to the guiding drum 21 through the torsion bar 23 and the respective ejector pins 37 so relative rotation thereof with respect to the guiding drum 21 is disabled. The webbing 3 is wound around an outer peripheral surface between the flange portion 27 of the guiding drum 21 and the flange portion 35 and the wire plate 25.

[Schematic Configuration of Take-Up Spring Unit]

Next, a schematic configuration of the take-up spring unit 8 will be described based on FIG. 2, FIG. 4 and FIG. 5.

As shown in FIG. 2, FIG. 4 and FIG. 5, the take-up spring unit 8 has a take-up urging mechanism 55 including a spiral spring, a spring case 56 for accommodating this take-up urging mechanism 55 and a spring shaft 58. The take-up spring unit 8 is fixed in the respective through holes 51 in the cover plate 57 constituting the outer side of the pretensioner unit 7 formed of a steel material or the like through nylon latches 8A provided at three locations on the spring case 56. A tip end portion of the drum shaft 22 in the take-up drum unit 6 is coupled with the spiral spring through the spring shaft 58 inside the spring case 56. Thus, the take-up drum unit 6 is urged in a retracting direction of the webbing 3 at all times owing to the urging force of the spiral spring.

[Schematic Configuration of Pretensioner Unit]

Next, a schematic configuration of the pretensioner unit 7 will be described based on FIG. 2, and FIG. 4 through FIG. 8.

FIG. 6 is a perspective view of the pretensioner unit 7 as seen from a housing unit 5 mounting side. FIG. 7 is a side view showing the pretensioner unit 7. FIG. 8 is an exploded perspective view showing the pretensioner unit 7 in FIG. 6 in a disassembled state.

As shown in FIG. 2, and FIG. 4 through FIG. 8, the pretensioner unit 7 is comprised of a pretensioner mechanism 17 and a forced locking mechanism 53 rotates a pawl 43 (refer to FIG. 9) which is rotatably supported at a side wall portion 12 of the housing unit 5.

[Pretensioner Mechanism]

As shown in FIG. 5 through FIG. 8, the pretensioner mechanism 17 activates a gas generating member 61 in case of vehicle collision. This causes the take-up drum unit 6 to rotate in the retracting direction of the webbing 3 through the flange portion 27 of the take-up drum unit 6, by using the pressure of this gas.

Here, the pretensioner mechanism 17 consists of: a gas generating member 61; a pipe cylinder 62; a sealing plate 63 and a piston 64 which move inside the pipe cylinder 62 under the gas pressure from the gas generating member 61; a pinion gear body 33 which engages a rack formed in this piston 64 and rotates; a base plate 65, to which the pipe cylinder 62 is mounted; a base block body 66 of a substantially rectangular shape which is in contact with the base plate 65 and mounted on a side surface of the pipe cylinder 62 on the pinion gear body 33 side; and a clutch mechanism 68 provided on a back surface of the base plate 65.

The pinion gear body 33 is provided with a pinion gear portion 71 and has a substantially cylindrical shape on an outer peripheral portion thereof. The pinion gear body 33 is made of a steel material or the like and engages the rack formed in the piston 64. The pinion gear body 33 also has a cylinder-shaped support portion 72 formed so as to extend outwardly from an end portion thereof on the cover plate 57 side, in an axial direction of the pinion gear portion 71. The support portion 72 is formed to have substantially the same length as the thickness of the cover plate 57, with the root diameter of the pinion gear portion 71 as outer diameter.

A flange portion 73 extending in a radial direction is formed at an end portion of the pinion gear portion 71 on the base plate 65 side in the axial direction thereof. Further, on the pinion gear body 33, there is formed a boss portion 74 which has a shaft receiving portion 33A formed in a substantially cylindrical-shape in an outward direction from the flange portion 73. The shaft receiving portion 33A is adapted for inserting therein the drum shaft 22 of the take-up drum unit 6 and fitting thereon the bearing 32. Three sets of splines having the outer diameter of the bottom end portion of the boss portion 74 are formed on an outer peripheral surface of this boss portion 74 at an interval of roughly 120° central angle.

The clutch mechanism 68 has a substantially annular-shaped pawl base 76 made of a steel material or the like, three clutch pawls 29 made of a steel material or the like, and a substantially annular-shaped pawl guide 77 which is made of a synthetic resin such as polyacetal resin or the like, and the pawl guide 77 and the pawl base 76 hold the respective clutch pawls 29 therebetween as will be described later.

On an inner peripheral surface of the pawl base 76 there are formed three sets of spline grooves at an interval of roughly 120° central angle. The spline grooves are press-fitted with the splines formed on the boss portion 74 of the pinion gear body 33. The pawl guide 77 is formed so that an inner peripheral diameter thereof is bigger than the spline grooves in the pawl base 76. Positioning projections 77A are provided at equal angles at three locations on the outer side face of the pawl guide 77 faced to the base plate 65.

The positioning projections 77A provided on the outer side face of the pawl guide 77 in the clutch mechanism 68 are engaged with the positioning holes 81 formed in the base plate 65, to set the clutch mechanism 68 to an outer surface of the base plate 65. Next, as shown in FIG. 8, the boss portion 74 of the pinion gear body 33 is inserted into the through hole 83 formed at substantially a central part of the base plate 65. Thereafter, the respective splines formed on the boss portion 74 is press-fitted and fixed in the respective spline grooves of the pawl base 76 constituting the clutch mechanism 68. As a result, the clutch mechanism 68 and the pinion gear body 33 are set and fixed to the base plate 65 and the pinion gear portion 71 of the pinion gear body 33 is positioned, at all times, in the position shown in FIG. 7.

The base block body 66 is made of a synthetic resin such as polyacetal resin or the like. The flange portion 73 of the pinion gear body 33 is inserted inside the through hole 82 formed on the bottom surface portion of the gear housing portion 85. This gear housing portion 85 is formed so as to be recessed in a substantially semicircle shape in plain view in an inward direction from a side edge portion inside the base block body 66 and also, is formed with a bottom surface thereof protruding outward (refer to FIG. 11). Positioning bosses 79 protruding at a side portion of the base block body 66 on the base plate 65 side are inserted into the positioning holes 80 formed in the base plate 65. The base block body 66 is thus set to a surface of the base plate 65 (refer to FIG. 6).

An elastic engagement piece 66A is formed so as to extend from an outer side surface of the base block body 66 to the base plate 65 side and enables elastic deformation thereof in an outward direction. An elastic engagement piece 66B is formed so as to extend from a lower-side side surface of the base block body 66 to the base plate 65 side and enables elastic deformation thereof in an outward direction (refer to FIG. 8). The elastic engaging pieces 66A and 66B latch with the respective side end portions of the base plate 65. As a result, the base block body 66 is set to the base plate 65.

The through hole 83 formed at a substantially central portion of the base plate 65 has an internal diameter which can support an outer diameter of the bottom end portion of the boss portion 74 in the pinion gear body 33. The through hole 83 is also formed so as to rotatably support the pinion gear body 33 with one end portion thereof. The gear housing portion 85 is formed so that a height thereof is substantially the same as the sum of heights of the pinion gear portion 71 and the flange portion 73 in the pinion gear body 33.

[Forced Locking Mechanism]

Here, the forced locking mechanism 53 set inside the base block body 66 will be described based on FIG. 5 through FIG. 8.

As shown in FIG. 7, a concave portion 86 for setting the forced locking mechanism 53 is formed in the base block body 66. In the base block body 66, there are provided a push block 87, a rotating lever 88, a block urging spring 87A, a gear-side arm 89 and an urging spring 90, which constitute the forced locking mechanism 53. The block urging spring 87A urges the push block 87 in the direction of the rotating lever 88. The urging spring 90 urges the gear-side arm 89 in the direction of the rotating lever 88. As shown in FIG. 6, to the gear-side arm 89, there are connected a coupling shaft 91 and a mechanical arm 92 which constitutes the forced locking mechanism 53 from outside the base plate 65.

The rotating lever 88 is made up of a synthetic resin such as polyacetal or an aluminum material or the like and is formed in a substantially L-shape, having through holes formed in a bending portion thereof. As shown in FIG. 7, the rotating lever 88 is rotatably supported by a boss 93 which is erected on the bottom surface of the concave portion 86 provided in the base block body 66, so that one end portion of the rotating lever 88 faces the pinion gear portion 71 of the pinion gear body 33.

The push block 87 is made up of a synthetic resin such as a polyacetal resin or the like. As shown in FIG. 7, the push block 87 is positioned so that one end thereof is in the vicinity of the teeth of the pinion gear portion 71 in the pinion gear body 33 and the other end thereof is in the vicinity of the rotating lever 88, by the positioning projections 94 erected in a bottom surface of the concave portion 86. The push block 87 is urged towards the rotating lever 88 by the block urging spring 87A so as to prevent looseness and making noise.

Accordingly, when the pinion gear body 33 is rotated as will be described later, the rotating lever 88 can be rotated in an outward direction (counter-clockwise direction in FIG. 7) by the push block 87 which is pushed against the teeth of the pinion gear portion 71 (refer to FIG. 11). The push block 87 is thus prevented from returning to the pinion gear body 33 side by the block urging spring 87A.

The gear-side arm 89 is made up of a synthetic resin such as polyacetal or the like or an aluminum material or the like and is formed in a substantially flat plate-shape. A boss 95 to be inserted in the through hole 96 formed in a bottom surface of the concave portion 86 in the base block body 66 is erected at one end portion of the gear-side arm 89 which is opposite to the other portion contacting with the rotating lever 88 at the side surface of the base block body 66. In a side surface onto which the boss 95 of the gear-side arm 89 is erected, there is formed a groove portion 97 which has a predetermined depth and allows for insertion of a bent portion formed at one end of the coupling shaft 91.

As shown in FIG. 6 and FIG. 8, the gear-side arm 89 has a stepped portion 98 formed at a tip end top surface of the rotating lever 88 so as to get in contact with the other end of the rotating lever 88. The boss 95 of the gear-side arm 89 is inserted in the through hole 96 which is formed at a bottom surface of the concave portion 86, and the gear-side arm 89 is rotatably supported toward the rotating lever 88 side. Further, the other tip end lower side of the gear-side arm 89 opposite to the stepped portion 98 is urged by the urging spring 90, and the gear-side arm 89 is urged towards the rotating lever 88 side (upward in FIG. 7). As a result, the stepped portion 98 will come in contact with the other end portion of the rotating lever 88.

Accordingly, if the rotating lever 88 is rotated in a counter-clockwise direction in FIG. 7, the other end portion of the rotating lever 88 moves away from the tip end portion of the gear-side arm 89 so that the gear-side arm 89 can rotate in an outward direction (counter-clockwise direction in FIG. 7) by the urging force of the urging spring 90.

The coupling shaft 91 is formed of a wire rod made up of a steel material or the like and is bent in a substantially right angle so that the ends thereof face each other with approximately 90-degree of tilt. The straight portion of this coupling shaft 91 is slightly longer than the width of the respective side wall portions 13 and 14 (refer to FIG. 9) of the housing unit 5.

As shown in FIG. 8, a groove 101 with the bent portion at one end of the coupling shaft 91 inserted therein extends from the through hole 96 formed in the bottom surface of the concave portion 86 of the base block body 66. A through hole 102 having a bent portion at one end of the coupling shaft 91 inserted therein is formed at a portion facing the gear-side arm 89 of the base plate 65.

Accordingly, the bent portion at one end of the coupling shaft 91 is guided through the through hole 102 of the base plate 65, the through hole 96 and the groove 101 of the base block body 66 to be fitted inside the groove portion 97 of the gear-side arm 89 installed inside the concave portion 86 of the base block body 66.

The mechanical arm 92 is made of a synthetic resin such as a polyacetal resin and the like or an aluminum material or the like and has a flat-plated and substantially fan-like shape, width of the fan-like shape being narrow. On its outer surface of the narrower one of the end portions, there is erected a boss 106 which can be rotatably fitted in the through hole 105 (refer to FIG. 9 and FIG. 10) formed in the side wall portion 12 (refer to FIG. 9) of the housing unit 5. Also, a boss 92A to be fitted inside a notch portion 138 (refer to FIG. 9) is erected on an outer surface at an outer peripheral edge portion of the mechanical arm 92 on the side wall portion 12 side. A groove portion 107 of a predetermined depth is formed along a center line in an inner surface of the mechanical arm 92.

Accordingly, as shown in FIG. 6, the bent portion at the other end of the coupling shaft 91 is fitted inside the groove portion 107 of the mechanical arm 92. The mechanical arm 92 is mounted to the other end side of the coupling shaft 91 so that the shaft center of the boss 106 erected in the outer side surface of an edge portion at the rotational axis of the mechanical arm 92 and the shaft center of the coupling shaft 91 become substantially straight.

If the pretensioner unit 7 is mounted to the housing unit 5 as will be described later, the boss 106 of the mechanical arm 92 is rotatably fitted inside the through hole 105 formed in the side wall portion 12 (refer to FIG. 10). The boss 92A of the mechanical arm 92 is inserted in the notch portion 138 formed in the side wall portion 12, so as to be rotatably mounted inside the side wall portion 12.

[Pretensioner Mechanism]

Next, the configuration and mounting of the pipe cylinder 62 constituting the pretensioner mechanism 17 will be described based on FIG. 5 through FIG. 8.

As shown in FIG. 5 through FIG. 8, the pipe cylinder 62 is formed of a steel pipe material or the like in a substantially L shape. The pipe cylinder 62 has a housing portion 62A having a substantially cylindrical shape formed at one end thereof (lower-side bent portion in FIG. 7). The pipe cylinder 62 is configured to house the gas generating member 61. This gas generating member 61 includes explosive powder which is ignited in response to an ignition signal transmitted from a control portion not shown, generating gas as a result of gas generating agent combustion.

At the other end of the pipe cylinder 62 (top-side bent portion in FIG. 7), there are formed a piston housing portion 62B having a substantially rectangular shape in cross section and a notch portion 111 at a portion thereof facing the pinion gear body 33. When the pipe cylinder 62 is installed on the base plate 65, the pinion gear portion 71 of the pinion gear body 33 is fitted inside this notch portion 111. At a top end portion of the piston housing portion 62B, there is formed a notch portion 113 which is engaged with an arm portion 112 bent at a substantially right angle from the base plate 65 at the side surface portion of the base block body 66 and functions as a slip-off prevention means of the pipe cylinder 62 in a vertical direction. A pair of through holes 114 which are relatively opposite each other and allow insertion of a stopper screw 16 are formed at opposite side surface portions of the pipe cylinder 62 and sideways from the notch portion 113. This stopper screw 16 is used for mounting the pretensioner unit 7 to the housing unit 5 and functions as a bounce-out prevention means of the piston 64.

As seen in FIG. 7 and FIG. 8, the sealing plate 63 is made of a rubber material or the like and formed as a substantially rectangular-shaped plate so as to allow insertion thereof from an top end portion of the piston housing portion 62B. The sealing plate 63 has a pair of projecting portions 63A which extend upwards at opposite edge portions in a longitudinal direction thereof and protrude inwardly over the full width of their respective top end portions. A gas releasing hole 63B is formed at a central part in the sealing plate 63.

The piston 64 is made of a steel material or the like and has an overall lengthy shape, with a substantially rectangular shape in cross section, allowing for insertion thereof from the top end portion of the piston housing portion 62B. At a lower end portion of the piston 63, there are formed engagement grooves 64A wherein respective projecting portions 63A of the sealing plated 63 are fitted from sideways. On the lower end surface of the piston 64, there is formed a thin communicating hole 64C which extends from the lower end surface of the piston 64 to a through hole 64B formed in a side surface portion of the piston 64.

After the respective projecting portions 63A of the sealing plate 63 are slid from sideways into to engagement grooves 64A of the piston 64 for fitting therein, the sealing plate 63 is installed inside and is press-fitted to the back side thereof in a depth direction from the top end of the piston housing portion 62B. The gas releasing hole 63B formed in the sealing plate 63 communicates with the through hole 64B through the communicating hole 64C of the piston 64.

Thus, in this state, the sealing plate 63 is depressed by the pressure of the gas generated in the gas generating member 61 and the piston 64 is caused to move to the top end opening portion (top end portion in FIG. 7) of the piston housing portion 62B. When the webbing 3 is pulled out again after the activation of the pretensioner as will be described later, the piston 64 drops downward due to the reverse rotation of the pinion gear body 33. The gas inside the pipe cylinder 62 is thus released through the gas releasing hole 63B of the sealing plate 63, the communicating hole 64C and the through hole 64B of the piston 64 and the piston 64 is caused to drop smoothly.

On the side surface of the pinion gear body 33 side of the piston 64, there is formed a rack 116 which engages the pinion gear portion 71 of the pinion gear body 33. At a back surface of a tip end portion of the rack 116 (top end portion in FIG. 7), there is formed a stepped portion 117 which can come in contact with the stopper screw 16. As shown in FIG. 7, in a normal state until the gas generating member 61 is activated, the piston 64 is positioned at the bottom of the piston housing portion 62B and the tip end of the rack 116 becomes disengaged from the pinion gear portion 71.

As shown in FIG. 7, the pipe cylinder 62 is installed on the base plate 65 in such a manner that the respective projecting portions 109 projecting outwardly from opposite edge portions of the gear housing portion 85 in the base block body 66 are being fitted inside the notch portion 111 of the thus configured piston housing portion 62B and the arm portion 112 of the base plate 65 is fitted inside the notch portion 113 formed in the top end portion of the piston housing portion 62B. A rack locking pin 108 having a substantially U-shape in cross section is erected in the base block body 66. The rack locking pin 108 is inserted in the gear groove at the top end of the rack 116 so as to restrain vertical movement of the piston 64. The tip end portion of the piston 64 is positioned in the vicinity of the pinion gear portion 71 of the pinion gear body 33, whereby the piston 64 is disengaged.

Thus, the opposite surfaces of the piston housing portion 62B in the pipe cylinder 62 are supported by ribs 110 and backrest portions 118A and 118B. The ribs 110 have a substantially triangular shape in cross section and are erected in a side surface of the base block body 66. The backrest portions 118A and 118B extend at a substantially right angle from portions on the side edge portions of the base plate 65 facing the pinion gear body 33. These backrest portions 118A and 118B extend slightly higher than the piston housing portion 62B and are formed so as to allow insertion thereof in the respective through holes 119A and 119B formed at side end portions of the cover plate 57 facing the backrest portions 118A and 118B.

The side edge portions of the through holes 119A and 119B facing the outside surfaces of the backrest portions 118A and 118B are recessed inwardly (leftward in FIG. 8) by a predetermined depth (for instance, approximately 1 mm deep). Thus, when the backrest portions 118A and 118B are inserted in the respective through holes 119A and 119B, the inner surface of the through holes 119A and 119B will reliably come in contact with the outside surface of the backrest portions 118A and 118B.

With the base block body 66, the forced locking mechanism 53 and the pipe cylinder 62 etc., being installed on the base plate 65, the positioning bosses 121 of this base block body 66 projecting in a side surface portion of the cover plate 57 are engaged with the respective positioning holes 122 of the cover plate 57. As a result, the cover plate 57 is installed on the top side of the base block body 66, the forced locking mechanism 53 and the pipe cylinder 62 etc. Simultaneously, a cylindrical support portion 72 of the pinion gear body 33 is fitted in a support hole 125 formed at a substantially center part in the cover plate 57.

The backrest portions 118A and 118B which extend substantially at a right angle from the side edge portions of the base plate 65 are inserted in the respective through holes 119A and 119B formed at side edge portions of the cover plate 57 facing the backrest portions 118A and 118B. Elastic engagement piece 66C and elastic engagement piece 66D are latched in the respective side end portions of the cover plate 57. The elastic engagement piece 66C extends from an outer side surface of the base block body 66 to the cover plate 57 side and is formed so as to be elastically deformable outwardly. The elastic engagement piece 66D extends from the top side surface of the base block body 66 to the cover plate 57 side and is formed so as to be elastically deformable outwardly.

Thus, the cover plate 57 is set and fixed to the base block body 65 and the pipe cylinder 62 is mounted between the cover plate 57 and the base plate 65. The support portion 72 formed at the end portion of the pinion gear body 33 is rotatably supported by the support hole 125 in the cover plate 57. Accordingly, as shown in FIG. 4, the support portion 72 and the bottom end portion of the boss portion 74 formed at opposite ends portions of the pinion gear body 33 are rotatably supported by the through hole 83 formed in the base plate 65 and the support hole 125 formed in the cover plate 57.

The through holes 114 of the pipe cylinder 62, the through hole 127 formed in the cover plate 57 at a position facing the through holes 114, and the screw hole 141B formed at a position facing the through holes 114 of the base plate 65 (refer to FIG. 9) are arranged coaxially. The stopper screw 16 formed of a steel material or the like can be inserted and threaded from the cover plate 57 side towards the base plate 65 side.

Accordingly, the pipe cylinder 62 is held between the cover plate 57 and the base plate 65 and also opposite side surfaces thereof are held by the base block body 66 and the backrest portions 118A and 118B. The top end opening of the piston housing portion 62B in the pipe cylinder 62 is covered by a cover portion 131 which extends from the top end portion of the cover plate 57 at a substantially right angle therewith. The sealing plate 63 is depressed under the pressure of the gas generated by the gas generating member 61 and the piston 64 is caused to move toward the top end opening portion (top end in FIG. 7) of the piston housing portion 62B. In this case, the stepped portion 117 of the piston 64 comes in contact with the stopper screw 16 inserted in the through holes 114 so as to stop thereat.

[Schematic Configuration of Housing Unit]

A schematic configuration of the housing unit 5 will next be described based on FIG. 4, FIG. 9 and FIG. 10.

FIG. 9 is an exploded perspective view of the housing unit 5. FIG. 10 is a side view showing the seatbelt retractor 1 with the locking unit 9 removed therefrom.

As shown in FIG. 9 and FIG. 10, the housing unit 5 is made of a housing 11, a bracket 133, a protector 135, a pawl 43 and a pawl rivet 136.

The housing 11 is made of a steel material or the like and is formed to have a substantially U-shape in plain view. In a back-side side wall portion 12 of the housing 11, there is formed a through hole 137 allowing for insertion of a tip end portion of the ratchet gear 26 in the take-up drum unit 6. A notch portion 138 is formed at an oblique lower side of the through hole 137 at a portion facing the pawl 43 so that the pawl 43 rotates smoothly. A through hole 139 is formed at the side of the notch portion 138 for mounting the pawl 43 in a rotatable fashion.

A semicircle-shaped guiding portion 140 is formed concentrically with the through hole 139 at a portion of the notch portion 138 which comes in contact with the pawl 43. The portion of the pawl 43 which comes in contact with and moves along the guiding portion 140 is formed to have approximately the same height as the thickness of the side wall portion 12. This portion has a stepped portion 43B which is recessed in a circular shape at a radius curvature which is the same as the side edge of the guiding portion 140 and is slightly higher than the thickness of the side wall portion 12. As shown in FIG. 10, a guiding pin 43A is erected in a tip end portion of an outer side surface of the pawl 43. The guiding pin 43A is inserted in a guiding groove (not shown) of the clutch (not shown) constituting the locking unit 9 as will be described later.

As shown in FIG. 9, side wall portions 13 and 14 which are relatively opposite to each other extend from opposite edge portions of the side wall portion 12. Opening portions are respectively formed at a center part in the side wall portions 13 and 14 so as to reduce weight and improve efficiency of the webbing mounting operation. Screwed portions 13A, 13B, 14A and 14B are formed at the top and lower edge portions of the side wall portions 13 and 14, respectively. These screwed portions extend inwardly by a predetermined depth, substantially at a right angle with the respective plates. Screw holes 141A wherein the respective screws 15 are screwed are formed in the respective screwed portions 13A, 13B and 14A by extruding. Screwed portion 141B wherein a stopper screw 16 is screwed is formed in the screwed portion 14B by extruding. It is to be noted that the screwed portion may be configured to be a through hole, through which the stopper screw 16 is inserted and fixed with a nut.

A bracket 133 mounted to the top edge portion of the side wall portion 13 by the respective rivets 134 is made of a steel material or the like. A horizontally long through hole 142 is formed at a portion extending from the top edge portion of the side wall portion 13 in an inward direction at a substantially right angle therewith, for pulling out the webbing 3 therefrom. A horizontally long frame-like protector 135 made of a synthetic resin such as nylon or the like is fitted inside the through hole 142. At the lower end portion of the side wall portion 13, there is formed a bolt insertion hole 132 in which a bolt 162 (refer to FIG. 10) is inserted at the time of mounting the housing 11 to a fastening piece 161 (refer to FIG. 10).

The stepped portion 43B of the pawl 43 made up of a steel material or the like is brought in contact with the guiding portion 140 and is rotatably fixed by the rivet 136 which is inserted in a rotatable fashion from the outside of the side wall portion 12 into the through hole 139. The side surface of the pawl 43 and the side surface of the ratchet gear 26 are positioned so as to be substantially coplanar with the outside surface of the side wall portion 12.

As shown in FIG. 10, in case the pretensioner unit 7 is mounted to the housing unit 5 through the screws 15 and the stopper screws 16, the boss 106 of the mechanical arm 92 which is mounted to the bent portion formed at the other end of the coupling shaft 91 is fitted in a rotatable fashion in the through hole 105 formed in the side wall portion 12. The boss 106 is thus positioned in the vicinity of the lower side surface of the pawl 43 as positioned inside the notch portion 138. The boss 92A erected in the outer side surface of the mechanical arm 92 is inserted in the notch portion 138. The pawl 43 will be in the vicinity of the mechanical arm 92 without being engaged with the ratchet gear 26 in normal operation.

As shown in FIG. 4, FIG. 9 and FIG. 10, an arm-protective extending portion 143 is arranged below the pawl 43 and the mechanical arm 92 installed in the side wall portion 12, at a position higher than the lower end face of the side wall portion 12 by a predetermined height (for instance, approximately 10 mm). The arm-protective extending portion 143 extends inwardly (leftward in FIG. 4) at a substantially right angle so as to face the pawl 43 and the mechanical arm 92 by a predetermined width (for instance, approximately 10 mm). In other words, below the pawl 43 and the mechanical arm 92 installed in the side wall portion 12, there is provided the arm-protective extending portion 143 having a predetermined width which extends inwardly by a predetermined length (for instance, approximately 10 mm) at a substantially right angle so as to face the mechanical arm 92.

As shown in FIG. 4, FIG. 9 and FIG. 10, a horizontally long opening portion 144A is formed in the side wall portion 13 at the position so as to face the coupling shaft 91 over substantially full length thereof. From the lower edge portion of this opening portion 144A, there is arranged a shaft-protective extending portion 144B which extends inwardly at a substantially right angle. The shaft-protective extending portion 144B extends so that its edge portion which is closer to the guide drum 21 is positioned deeper from the coupling shaft 91 which faces the side wall portion 13. Further, below this shaft-protective extending portion 144B, there is formed the bolt insertion hole 132 through which the bolt 162 is inserted and fixed to the fastening piece 161 of the vehicle with the nut 163.

[Description of Operation of Forced Locking Mechanism and Pawl]

Next, the operation of the forced locking mechanism 53 and the pawl 43 when activated by the gas generating member 61 of the pretensioner mechanism 17 in case of a vehicle collision will be described based on FIG. 11 and FIG. 12. FIG. 11 is an explanatory diagram showing the state that the piston 64 is moved further in response to the activation of the gas generating member in the pretensioner mechanism 17 and the lower end portion of the rotating lever 88 is disengaged from the tip end portion of the gear-side arm 89. FIG. 12 is an explanatory diagram showing the operation of the pawl 43 corresponding to FIG. 11.

As shown in FIG. 11, in case the gas generating member 61 of the pretensioner mechanism 17 is activated in case of a vehicle collision or the like, the piston 64 inside the piston housing portion 62B of the pipe cylinder 62 shears the rack locking pin 108 from a normal state as shown in FIG. 7 and moves upwards (direction arrow X1) so as to cause the pinion gear body 33 rotate in a counter-clockwise direction in front view (direction of arrow X2). As the top end portion of the rotating lever 88 is further depressed by the push block 87 which was depressed by the block urging spring 87A, the lower end portion of this rotating lever 88 is disengaged from the tip end portion of the gear-side arm 89.

The gear-side arm 89 is depressed in an outward direction by the urging spring 90 and rotated in a counter-clockwise direction in front view (direction of arrow X4). The push block 87 is depressed in an outward direction by the block urging spring 87A to be kept disengaged from the pinion gear portion 71 of the pinion gear body 33 and makes the top end portion of the rotating lever 88 kept in contact with the internal wall surface of the concave portion 86.

As shown in FIG. 12, in case the lower end portion of the rotating lever 88 is disengaged from the tip end portion of the gear-side arm 89, this gear-side arm 89 is rotated in a counter-clockwise direction in front view (direction of arrow X5). This will cause the coupling shaft 91, with the bent portion formed at one end thereof being inserted inside the groove 97 of the gear-side arm 89, to rotate in a counter-clockwise direction as seen from a front view around a center axis (direction of arrow X5).

As the bent portion at the other end portion of the coupling shaft 91 is inserted in the groove portion 107, the mechanical arm 92 is rotated in a counter-clockwise direction as seen from a front view (direction of arrow X5) in response to rotation of the gear-side arm 89. This causes the pawl 43 to engage the ratchet gear portion 45 of the ratchet gear 26. The pawl 43 and the ratchet gear portion 45 of the ratchet gear 26 are engaged so as to restrain rotation of the take-up drum unit 6 in the webbing-pull-out direction and allow rotation in the retracting direction of the webbing 3.

Accordingly, in case the pawl 43 and the ratchet gear portion 45 of the ratchet gear 26 are engaged, a locking operation is carried out to restrain rotation of the take-up drum unit 6 in a pull out direction of the webbing 3, and rotation in the retracting direction of the webbing 3 is allowed. Thus, the pawl 43 can restrain rotation of the take-up drum unit 6 in a pull out direction of the webbing 3 before the clutch mechanism 68 and the pinion gear body 33 start rotating together.

After rotation of the pinion gear body 33 is stopped following activation of the pretensioner mechanism 17, the lower end portion of the rotating lever 88 is kept away from the tip end portion of the gear-side arm 89, as shown in FIG. 15. After the pretensioner mechanism 17 has been activated, the pawl 43 and the ratchet gear portion 45 of the ratchet gear 26 are kept engaged. Thus, the ratchet gear 26 and the wire plate 25 of the take-up drum unit 6 are restrained from rotating in the pull out direction of the webbing 3.

As was described in detail earlier, in the seatbelt retractor 1 according to the present embodiment, the side wall portion 12 of the housing 11 is provided with, below the pawl 43 and the mechanical arm 92, the arm-protective extending portion 143 which extends inwardly at a substantially right angle. The side wall portion 13 of the housing 11 is provided with the shaft-protective extending portion 144B which extends inwardly at a substantially right angle from the lower edge portion of the horizontally long opening portion 144A which is formed so as to face substantially full length of the coupling shaft 91. Below this shaft-protective extending portion 144B, there is formed the bolt insertion hole 132 through which the bolt 162 is inserted at the time of mounting the housing 11 to the fastening piece 161 of the vehicle.

Therefore, at the time of mounting the seatbelt retractor 1 to the fastening piece 161 of the vehicle, the shaft-protective extending portion 144B can prevent contact between the upper edge portion of the fastening piece 161 and the coupling shaft 91, and the arm-protective extending portion 143 can prevent contact between the upper edge portion of the fastening piece 161 and the mechanical arm 92 or the pawl 43. As a result, it is possible to improve working efficiency of mounting the seatbelt retractor 1 to the fastening piece 161 and reliability thereof.

If the gas generating member 61 of the pretensioner mechanism 17 is activated in case of vehicle collision, the piston 64 is moved upwards inside the piston housing portion 62B of the pipe cylinder 62 from a normal state and comes in contact with the pinion gear portion 71 of the pinion gear body 33, whereby the pinion gear body 33 is caused to rotate. As a result, as the teeth of the pinion gear portion 71 in the pinion gear body 33 push the push block 87. Therefore, this push block 87 shears the positioning projection 94 erected on the bottom surface of the base block body 66. The push block 87 which has sheared the positioning projection 94 is pushed by the block urging spring 87A and comes in contact with the tip end portion of the rotating lever 88, whereby the rotating lever 88 is pushed and rotated. Thus, the lower end portion of the rotating lever 88 is disengaged from the tip end portion of the gear-side arm 89. The gear-side arm 89 is thus rotated in an outer direction by the urging spring 90, and simultaneously, the mechanical arm 92 is rotated through the coupling shaft 91. As a result, the pawl 43 engages the ratchet gear portion 45 of the ratchet gear 26 in the take-up drum unit 6.

If the gas generating member 61 of the pretensioner mechanism 17 is activated in case of vehicle collision, the pawl 43 is directly rotated by the push block 87, the block urging spring 87A, the rotating lever 88, the gear-side arm 89, the coupling shaft 91 and the mechanical arm 92 substantially simultaneously with rotation of the pinion gear body 33 by the piston 64, so as to engage the ratchet gear 26 of the take-up drum unit 6. Thus, the pawl 43 engages the ratchet gear 26 of the take-up drum unit 6 substantially simultaneously with activation of the pretensioner mechanism 17. As a result, the take-up drum can be locked in so as to prevent rotation thereof in the direction for the webbing 3 to be pulled out swiftly and reliably, whereby the operation to pull out the webbing 3 by vehicle occupants and a drop in the belt load can be prevented.

The present invention is not limited to the above-described embodiment, but various improvements and alterations can be made thereto without departing from the spirit of the present invention. 

The invention claimed is:
 1. A seatbelt retractor comprising: a take-up drum onto which a webbing is wound and housed; a housing which includes a first side wall portion and a second side wall portion facing the first side wall portion, and rotatably supports the take-up drum in between the first side wall portion and the second side wall portion; and a pretensioner assembly which rotates the take-up drum in a retracting direction to retract the webbing in case of vehicle collision, wherein the pretensioner assembly includes a driving device which is mounted to an outside of the first side wall portion of the housing and causes the take-up drum to rotate in the retracting direction of the webbing in case of the vehicle collision, wherein the take-up drum includes: a ratchet gear formed on a periphery of an edge portion of the take-up drum which so as to face an inside of the second side wall portion of the housing; a pawl arranged at a position where the pawl is disengaged from the ratchet gear while one end of the pawl is rotatably supported at the inside of the second side wall portion of the housing; and a locking device which is directly activated by the driving device upon activation of the driving device and locks the pawl in an engaged state with the ratchet gear, wherein the locking device, includes: an arm member one end of which is rotatably supported at an outside of the first side wall portion of the housing; a rotating device which is provided at the outside of the first side wall portion of the housing and is directly activated by the driving device so as to cause the arm member to rotate in a predetermined direction; a depressing member which is in contact with the pawl at one side face which is opposed to other side face thereof which is closer to the ratchet gear while one end of the depressing member is rotatably supported at the inside of the second wall portion of the housing; and a coupling shaft which couples the arm member and the depressing member, and wherein the housing includes: a third wall portion which is opposed to a periphery of the coupling shaft; a bolt insertion hole which is formed in an opposite end portion of the third wall portion with respect to a pull-out direction of the webbing, the bolt insertion hole being provided for mounting the housing to a vehicle; a first extending portion for protecting the coupling shaft which extends from the inside of the third wall portion so as to be opposed to a side of the coupling shaft which is closer to the bolt insertion hole.
 2. The seatbelt retractor according to claim 1, wherein the housing includes a second extending portion for protecting the depressing member which extends from the inside of the second side wall portion of the housing so as to protect one side face of the depressing member which is opposed to other side face thereof which is closer to the pawl. 